The present invention relates to a control device for a vehicle stopping at a slope road having an electric motor as a power source. More particularly, the present invention pertains to a control device for a vehicle stopping at a slope road under a condition that a drive torque of an electric motor is generated.
Electric motors, which serve as power sources for electric vehicles, are supplied with the electric power from in-vehicle batteries. Because limited electric energy is charged in the battery installed in the vehicle, the mileage of the electric vehicle per charge of the battery installed in the vehicle is limited.
In order to deliver more mileage of the electric vehicle per charge of the battery installed in the vehicle, not only a hydraulic brake by a braking hydraulic pressure but also a regenerative braking force generated at driving wheels when recovering the electric power, which is generated in the electric motor by the rotation of the driving wheels, into the battery installed in the vehicle is maximally applied at braking the electric vehicle according to known devices. With the application of the regenerative braking force, because the electric power corresponding to the generated regenerative braking force is recovered into the battery installed in the vehicle, more mileage of the electric vehicle per charge of the battery installed in the vehicle is delivered.
Notwithstanding, in order to further increase mileage of the electric vehicle per charge of the battery installed in the vehicle, it is important to reduce the electric power consumption per se in the battery installed in the vehicle by the operation of the electric motor while utilizing the regenerative, braking force.
Under the condition that the vehicle is at stopping state on the slope road while balancing the drive torque and the down-sloping directional component of the gravity generated relative to the vehicle when the drive torque of the electric motor is generated by operating a throttle pedal, the electric power in the battery installed in the vehicle is consumed for generating the drive torque of the electric motor irrespective of the stopping state of the vehicle. This condition is expected to be caused particularly when the traffic congestion is caused on the slope road and when an operator is waiting at stoplights on the slope road. This is because the operator can control a stop and a start of the vehicle by adjusting the depression amount of the throttle pedal instead of operating the brake pedal when the vehicle is stopping at the slope road.
The electric power consumed under the foregoing condition does not contribute to the vehicle driving, and thus the electric power consumption under the foregoing condition is required to be reduced.
A need exists for a control device for an electric vehicle stopping at a slope road which enables to reduce the electric power consumption of an electric motor in case the electric vehicle is stopped on the slope road under a state that a drive torque of the electric motor is generated.
In light of the foregoing, the present invention provides a control device for an electric vehicle stopping at a slope road which includes an electric motor for driving a wheel, a drive torque control means for controlling a drive torque of the electric motor in accordance with a driving condition of the vehicle and outputting the drive torque to the electric motor, a hydraulic brake force adjusting means for adjusting a hydraulic brake force for applying a hydraulic pressure to a wheel cylinder of the wheel independent from a brake pedal operation, and a judging means for a stopping state at a slope road which judges whether the vehicle is under a stopping state at a slope road when the drive torque is equal to or greater than the predetermined value. When the judging means for the stopping state at the slope road judges that the vehicle is under the stopping state at the slope road, the hydraulic brake force adjusting means applies a predetermined hydraulic pressure to the wheel cylinder of the wheel and the drive torque control means decreases a drive torque outputted to the electric motor to be lower than a drive torque controlled in accordance with a driving condition of the vehicle.